Semiconductor wafers are transferred to locations where processes (e.g., cleaning, deposition, etching, etc.) are carried out. Therefore, various wafer transfer apparatuses have been used.
Generally, wafer transfer apparatuses used at an atmospheric pressure fix substrates using vacuum. Since a wafer transfer apparatus used in a high vacuum system cannot use vacuum, a shoe is mounted on front and rear edges of a plate on which a wafer is placed. Thus, wafers may be separated from blades when they are transferred at a high speed. Further, there was no method for correcting wafers that are disposed to swerve from blades.
In recent years, means for clamping wafers placed on blades have been developed so as to fix the wafers stably. Nevertheless, the clamping means has a complex structure and thus it is hard to regulate the structure of the clamping means. Moreover, wafers may be damaged by the clamping means.